Upon winning the Thameslink, Southern and Great Northern franchise Govia Thameslink Railway (GTR) announced that it would seek to replace the existing units (which are currently 40 years old as of 2016) currently operating on services to and from Moorgate, with up to 25 six-car units intended to be procured. In December 2015 GTR announced that it had selected Siemens to provide this new fleet as a follow-on order from the main Class 700 order - with entry into service expected from 2018. The order was finalised in February 2016.